In known headphone technology, the driver units of various types of headphones outputting sound wave also incur an electrical output with respect to the pressure resist changes on the front and rear cavities of the diaphragm, for example, donned, doffed, or vibration (such as, fingertip tapping the headphone case). In other words, because of the diaphragm displacement caused by force resulting in a change in magnetic field, a current signal is generated. However, at present, the generated current signal is viewed as an additional signal other than the audio playback signal, and is not used or applied.
For the current usage status detection of headphones, US Publication No. 20150281825 A1 disclosed a headphone on-head detection using differential signal measurement, which described how additional microphones (element 114/124 in FIG. 1) are used as a sensor, but the current signal generated by the displacement of the headphone driver unit diaphragm is not utilize or applied.
Taiwan Patent No. I522902 disclosed an “Electronic Device and Headphone Sensing Method”, applicable to an electronic device having a headphone jack, which includes a conductive plug for detecting whether or not the headphone jack is inserted with a speaker device; when the conductive plug is inserted into the headphone jack, the microphone contact point of the conductive plug records to generate a recording result and determines whether an audio signal is included in the recording result; and when the recording result includes the audio signal, the speaker device is determined to provide a microphone function.
Taiwan Patent No. I316401 disclosed a “Headphone ECG Measurement System”, providing a headphone-sensing heart-rate measurement system for convenient, comfort and non-invasive ECG measurement. The ECG measurement system comprises an ECG signal analysis device and a headphone sensing device. The ECG signal analysis device comprises an amplifier module, a micro controller, a display, a radio module and a shell with conductive contacts. The headphone sensing device includes a headphone and an electrode arranged in the headphone, and electrically connectable to a user for collecting the weak ECG signal of the user's head, to form a basic circuit with the shell having conductive contacts and the user's body surface contacting the electrode for collecting the ECG signals.
Taiwan Patent No. 201422204 disclosed “Acquiring physiologic measurements using a sensor at the ear”, providing a device and method for acquiring one or more physiological measurements associated with a user using a sensor located at the ear. One or more different types of sensors are configured to engage a user's ear; wherein the sensors are contained in one or both of ear-pieces of the headphones to capture physiological parameters. A portable device is configured to communicate with the sensors to receive physiological parameters and provide control signals to the sensors or other elements in the headphone. And the portable device determines physiological measurements corresponding to the received physiological parameters, and the portable device is also configured to provide a user interface to interact with the user regarding the physiological measurements.
Therefore, the issues need to be addressed include how to use a headphone driver unit diaphragm used as a sensor, by analyzing the headphone wear status to use the electric output signal generated by the pressure resist changes on the front and rear cavities of the diaphragm; in other words, a current signal generated because of the diaphragm displacement caused by force resulting in a change in magnetic field; and how to extract the sensed signal generated by the diaphragm passively sensed during headphone playback without using additional microphone element and use the extracted sensed signal for subsequent analysis and auto-control and/or signal compensation reference source.